I went to a non-Jewish self-catering apartment and I was discussing with my friend whether we can use the utensils or not. Of course, if they are clean and used for cold there are no problems. We started debating whether it is considered a minhag not to use these types of utensils anyway.
At what point do things become minhag yisrael (the practice of Jews)? Furthermore, if the minhag is based false premises can it be uprooted or does it need hatarat nedarim (vow annulment)?